Water quality in water lines of dental units in the public dental health service in Göteborg, Sweden.

Presence of bacteria in high levels in the water lines of dental units is well known. The extent of this problem is however less well studied.This study was conducted to evaluate the water quality of all dental units within the Public Dental Health Service (Folktandvården, FTV) of the city of Göteborg, Sweden. 405 dental units in 35 clinics were tested.The evaluation included both "fast growing" (2 days incubation) and "slow growing" (7 days incubation) bacteria in 50 ml water sample from the units. The presence of potential pathogens, e.g., coliforms, Pseudomonas spp and Legionella pneumophila were also examined. Of the 405 dental units, 303 (75%) did not have acceptable (<100 CFU/ml fast growing and <5000 CFU/ml of slow growing bacteria) water quality. From 61 (15%) dental units in 13 clinics L. pneumophila were present but usually as few cells only. Immediate measures were introduced in Legionella positive units. No coliforms or Pseudomonas spp were detected. It can be concluded that the water in the dental units is generally not acceptable and does not fulfill drinking water standard. Many units have extremely high bacterial levels, which must be regarded as a risk for certain patient groups, e.g., immune-compromised and older patients. A general program for desinfection of all units of the Public Dental Health Service is needed.